Aims: Lower vertebrates and some neonatal mammals are known to possess the ability to regenerate cardiomyocyte and fully recover after heart injuries within a limited period. Understanding the molecular mechanisms of heart regeneration and exploring new ways to enhance cardiac regeneration hold significant promise for therapeutic intervention of heart failure. Sphingosine 1-phospahte receptor 1 (S1PR1) is highly expressed in cardiomyocytes and plays a crucial role in heart development and pathological cardiac remodeling. However, the effect of cardiomyocyte-expressing S1PR1 on heart regeneration has not yet been elucidated. This study aims to investigate the role of cardiomyocyte S1PR1 in cardiac regeneration following heart injuries. Methods and Results: We generated cardiomyocyte (CM)-specific S1pr1 knock-out mice and demonstrated that CM-specific S1pr1 loss-of-function severely reduced cardiomyocyte proliferation and inhibited heart regeneration following apex resection in neonatal mice. Conversely, AAV9-mediated CM-specific S1pr1 gain-of-function significantly enhanced cardiac regeneration. We identified that S1PR1 activated the AKT/mTORC1/CYCLIN D1 and BCL2 signaling pathways to promote cardiomyocyte proliferation and inhibit apoptosis. Moreover, CM-targeted gene delivery system via AAV9 to overexpress S1PR1 significantly increased cardiomyocyte proliferation and improved cardiac functions following myocardial infarction in adult mice, suggesting a potential method to enhance cardiac regeneration and improve cardiac function in the injured heart. Conclusions: This study demonstrates that CM-S1PR1 plays an essential role in cardiomyocyte proliferation and heart regeneration. This research provides a potential strategy by CM-targeted S1PR1 overexpression as a new therapeutic intervention for heart failure.
© The author(s).

GM-CSF has been employed as an adjuvant to cancer immunotherapy with mixed results based on dosage. We previously showed that GM-CSF regulated tumor angiogenesis by stimulating soluble vascular endothelial growth factor (VEGF) receptor-1 from monocytes/macrophages in a dose-dependent manner that neutralized free VEGF, and intratumoral injections of high-dose GM-CSF ablated blood vessels and worsened hypoxia in orthotopic polyoma middle T Ag (PyMT) triple-negative breast cancer (TNBC). In this study, we assessed both immunoregulatory and oxygen-regulatory components of low-dose versus high-dose GM-CSF to compare effects on tumor oxygen, vasculature, and antitumor immunity. We performed intratumoral injections of low-dose GM-CSF or saline controls for 3 wk in FVB/N PyMT TNBC. Low-dose GM-CSF uniquely reduced tumor hypoxia and normalized tumor vasculature by increasing NG2+ pericyte coverage on CD31+ endothelial cells. Priming of "cold," anti-PD1-resistant PyMT tumors with low-dose GM-CSF (hypoxia reduced) sensitized tumors to anti-PD1, whereas high-dose GM-CSF (hypoxia exacerbated) did not. Low-dose GM-CSF reduced hypoxic and inflammatory tumor-associated macrophage (TAM) transcriptional profiles; however, no phenotypic modulation of TAMs or tumor-infiltrating lymphocytes were observed by flow cytometry. In contrast, high-dose GM-CSF priming increased infiltration of TAMs lacking the MHC class IIhi phenotype or immunostimulatory marker expression, indicating an immunosuppressive phenotype under hypoxia. However, in anti-PD1 (programmed cell death 1)-susceptible BALB/c 4T1 tumors (considered hot versus PyMT), high-dose GM-CSF increased MHC class IIhi TAMs and immunostimulatory molecules, suggesting disparate effects of high-dose GM-CSF across PyMT versus 4T1 TNBC models. Our data demonstrate a (to our knowledge) novel role for low-dose GM-CSF in reducing tumor hypoxia for synergy with anti-PD1 and highlight why dosage and setting of GM-CSF in cancer immunotherapy regimens require careful consideration.
Copyright © 2023 by The American Association of Immunologists, Inc.

SUMMARY Group A Streptococcus (GAS) infections can cause neuropsychiatric sequelae in children due to post-infectious encephalitis. Multiple GAS infections induce migration of Th17 lymphocytes from the nose into the brain, which are critical for microglial activation, blood-brain barrier (BBB) and neural circuit impairment in a mouse disease model. How endothelial cells (ECs) and microglia respond to GAS infections, and which Th17-derived cytokines are essential for these responses are unknown. Using single-cell RNA sequencing and spatial transcriptomics, we found that ECs downregulate BBB genes and microglia upregulate interferon-response, chemokine and antigen-presentation genes after GAS infections. Several microglial-derived chemokines were elevated in patient sera. Administration of a neutralizing antibody against interleukin-17A (IL-17A), but not ablation of granulocyte-macrophage colony-stimulating factor (GM-CSF) in T cells, partially rescued BBB dysfunction and microglial expression of chemokine genes. Thus, IL-17A is critical for neuropsychiatric sequelae of GAS infections and may be targeted to treat these disorders.

The ideal scaffold material of angiogenesis should have mechanical strength and provide appropriate physiological microporous structures to mimic the extracellular matrix environment. In this study, we constructed an integrated three-dimensional scaffold material using porous tantalum (pTa), gelatin nanoparticles (GNPs) hydrogel, and seeded with bone marrow mesenchymal stem cells (BMSCs)-derived endothelial cells (ECs) for vascular tissue engineering. The characteristics and biocompatibility of pTa and GNPs hydrogel were evaluated by mechanical testing, scanning electron microscopy, cell counting kit, and live-cell assay. The BMSCs-derived ECs were identified by flow cytometry and angiogenesis assay. BMSCs-derived ECs were seeded on the pTa-GNPs hydrogel scaffold and implanted subcutaneously in nude mice. Four weeks after the operation, the scaffold material was evaluated by histomorphology. The superior biocompatible ability of pTa-GNPs hydrogel scaffold was observed. Our in vivo results suggested that 28 days after implantation, the formation of the stable capillary-like network in scaffold material could be promoted significantly. The novel, integrated pTa-GNPs hydrogel scaffold is biocompatible with the host, and exhibits biomechanical and angiogenic properties. Moreover, combined with BMSCs-derived ECs, it could construct vascular engineered tissue in vivo. This study may provide a basis for applying pTa in bone regeneration and autologous BMSCs in tissue-engineered vascular grafts.
© The Author(s) 2021. Published by Oxford University Press.

Skeletal muscle has remarkable regenerative ability after injury. Mesenchymal fibro-adipogenic progenitors (FAPs) are necessary, active participants during this repair process, but the molecular signatures of these cells and their functional relevance remain largely unexplored. Here, using a lineage tracing mouse model (Gli1-CreER Tomato), we demonstrate that Gli1 marks a small subset of muscle-resident FAPs with elevated Hedgehog (Hh) signaling. Upon notexin muscle injury, these cells preferentially and rapidly expanded within FAPs. Ablation of Gli1+ cells using a DTA mouse model drastically reduced fibroblastic colony-forming unit (CFU-F) colonies generated by muscle cells and impaired muscle repair at 28 days. Pharmacologic manipulation revealed that Gli1+ FAPs rely on Hh signaling to increase the size of regenerating myofiber. Sorted Gli1+ FAPs displayed superior clonogenicity and reduced adipogenic differentiation ability in culture compared to sorted Gli1- FAPs. In a glycerol injury model, Gli1+ FAPs were less likely to give rise to muscle adipocytes compared to other FAPs. Further cell ablation and Hh activator/inhibitor treatments demonstrated their dual actions in enhancing myogenesis and reducing adipogenesis after injury. Examining single-cell RNA-sequencing dataset of FAPs from normal mice indicated that Gli1+ FAPs with increased Hh signaling provide trophic signals to myogenic cells while restrict their own adipogenic differentiation. Collectively, our findings identified a subpopulation of FAPs that play an essential role in skeletal muscle repair. © 2021 American Society for Bone and Mineral Research (ASBMR).
© 2021 American Society for Bone and Mineral Research (ASBMR).